Wasn't this literally Reddit's game plan?

I don't think so. Far as I can remember Reddit decided to lock down their site and start monetizing user data. They don't and never have had any sort of widely used authentication like googles SSO and Email combo. Far as I can see Meta and Google are the main "Real users" players at least in the wider internet ad markets.

Actual Identity companies have almost no presence outside of banking/finance/gov from what I see.